The invention relates to a method and a radio communications system for assigning a frequency channel to a radio station, in particular for radio communications systems which contain a plurality of possibly non-coherent frequency bands and an appropriate radio station.
Published, British Patent Application GB 2 311 910 A describes a method for assigning a frequency channel to a radio station of a radio communications system and to a radio communications system.
In radio communications systems, messages (for example voice, image information or other data) are transmitted using electromagnetic waves. The irradiation of the electromagnetic waves takes place here at carrier frequencies that lie in the frequency band provided for the respective system. In the case of a global system for mobile communication (GSM), the carrier frequencies lie in the region of 900 MHz, 1800 MHz or 1900 MHz, further standards (NMT, IS-95, etc.) using in turn identical or additional frequency bands. For future radio communications systems, for example the universal mobile telecommunication system (UMTS) or other 3rd generation systems, frequencies in the frequency band of approximately 2000 MHz are provided.
Between a transmitting and a receiving radio station there is a radio interface over which a data transmission takes place using the electromagnetic waves. Published, Non-Prosecuted German Patent Application DE 197 33 336 A1 discloses a radio communications system which uses a CDMA subscriber separation (CDMA Code Division Multiple Access), the radio interface additionally having a time division multiple subscriber separation (TDMA Time Division Multiple Access). At the receiving end, a joint detection (JD) method is applied in order to perform improved detection of the transmitted data with spread codes of a plurality of subscribers being known.
From the GSM mobile radio network it is known that a number is transmitted from a base station to the mobile station in order to assign a frequency channel to a mobile station, the number designating, as a multiple of the fixed standard bandwidth of 200 kHz, the frequency channel which is to be selected in the uplink direction, for example for GSM900 the numbers 0 . . . 123 within the frequency band from 890-915 MHz. This numbering is valid only for this frequency band and for the GSM1800 frequency band with numbers 512 . . . 885; in other GSM frequency bands, for example for PCS1900 or for mobile radio networks with other transmission methods the numbering scheme is not unambiguous, or is defined in other ways in other standards.
This leads to ambiguities in multi-mode mobile radio stations or in future third generation mobile radio stations because a plurality of frequency bands are available and possibly different bandwidths of the frequency channels are made available.
It is accordingly an object of the invention to provide a method and a radio communications system for assigning a frequency channel to a radio station and an appropriate radio station that overcome the above-mentioned disadvantages of the prior art devices and methods of this general type, which simplify the assignment of a frequency channel to a mobile station.
With the foregoing and other objects in view there is provided, in accordance with the invention, a method for assigning a frequency channel to a radio station of a radio communications system, which includes:
transmitting a signaling message from a first radio station to a second radio station, the signaling message containing a number of the frequency channel for defining a signaled frequency channel and information relating to a bandwidth of the frequency channel, the number of the frequency channel and the information relating to the bandwidth of the frequency channel refer to a common standard bandwidth, and both the number of the frequency channel and the information relating to the bandwidth are contained, in a form of multipliers of the common standard bandwidth in the signaling message;
receiving the signaling message in the second radio station; and
the second radio station using the signaled frequency channel for transmission and reception purposes.
In the method according to the invention for assigning the frequency channel to the radio station of a radio communications system, the signaling message is transmitted from the first radio station to the second radio station. The signaling message contains information relating to the number of the frequency channel and to the bandwidth of the frequency channel, and both the number of the frequency channel and the bandwidth of the frequency channel refer to a common standard bandwidth. The signaling message is received by the second radio station and the signaled frequency channel is used for transmission and/or reception purposes. The data relating to the number and to the bandwidth of the frequency channel unambiguously indicate the frequency channel to be used, even in the case of radio communications systems having a plurality of non-coherent frequency bands. Any desired transmission method may be used in the individual frequency bands here. A further advantage consists in the fact that it is not necessary to start from a single bandwidth that has been defined in advance, but rather the bandwidth can be assigned and signaled after an appropriate request. The assignment is thus significantly more flexible.
According to one advantageous refinement, the bandwidth is equal to the standard bandwidth or a multiple thereof. This simplifies the signaling because the bandwidth can be signaled by an integer that is to be multiplied by the standard bandwidth. According to a further embodiment of the invention, the second radio station selects the standard bandwidth as the bandwidth to be used if the information relating to the bandwidth is not present in the signaling message. This is significant in particular for downlink compatibility between components of different generations of radio communications systems. Thus, for example a base station of a GSM mobile radio network can continue to transmit a number which indicates only the number of the frequency band, which number is also processed by mobile stations which expect frequency channel assignments according to the invention. The scheme according to the invention can therefore be implemented in existing signaling mechanisms.
According to a further advantageous refinement of the invention, the number indicates the frequency channel whose distance from a reference channel is equal to the standard bandwidth or a multiple thereof. It is thus possible to restrict the signaling to integers that, once multiplied by the standard bandwidth and provided with the reference frequency as an offset, unambiguously describe the frequency channel.
The number here indicates the start (lowest or highest frequency) of the frequency channel or the center of the frequency channel. The reference frequency can additionally be signaled, but it is advantageously defined and stored in both radio stations. Further signaling complexity is thus eliminated. The numbering of a frequency band does not need to start at zero here, but instead predefinable number ranges can advantageously also be assigned to individual frequency ranges.
There are a plurality of possible ways of defining the standard bandwidth. If a migration from the GSM mobile radio network is aimed at, the standard bandwidth is advantageously equal to 200 kHz. If further networks that use a relatively small bandwidth of the frequency channels are to be included, it is advantageous if the standard bandwidth is equal to the smallest of the carrier bandwidths of the different radio communications networks. If the different bandwidths that are to be used cannot be related back to a minimum common divisor, the standard bandwidth is equal to the most frequently expected bandwidth. The signaling is thus simplest for these most frequently occurring cases. Alternatively, the bandwidth can also be signaled as a selection from a plurality of available bandwidths. If only a few bandwidths are available for selection, only a small number of bits are necessary for signaling.
Other features which are considered as characteristic for the invention are set forth in the appended claims.
Although the invention is illustrated and described herein as embodied in a method and a radio communications system for assigning a frequency channel to a radio station and an appropriate radio station, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.
The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.